1. Field of the Invention
The present invention relates to a slot-less motor, and more particularly to a slot-less motor for super high speed driving for easily obtaining an air gap flux density and preventing a stator coil from being separated.
2. Description of the Prior Art
Generally, a slot-less motor is used as an appropriate device for a motor for super high speed driving because it can easily make distribution of field magnetic flux to an ideal sinusoidal wave.
The slot-less motor includes as illustrated in FIGS. 4 and 5, a cylindrical housing 50 forming a stator, a stator coil 51 wound in a predetermined shape within the housing 50 for being tightly secured thereinto, a magnet 53 mounted at an outer surface of a rotor shaft 52 in order to maintain a predetermined distance of air gap (d) from the stator coil 51 and a housing cap 55 secured at both sides of the housing 50 in order to support both ends of the rotor shaft 52 by bearings 54.
The stator coil 51 is not provided with a slot at the housing 50 for its winding and fixing, such that the stator coil 51 is wound beforehand in a predetermined shape, secured at an inner surface of the housing 50, and bonded as such or impregnated in adhesive materials such as bond 56 and the like to thereafter be fixed therein. Particularly in this case, the air gap (d) between the magnet 53 of a rotor and the coil 51 which determine a rotary speed and torque of a rotor during fixation of the stator coil 51 should maintain a relatively wide breadth in order to adapt to high speed.
Furthermore, the stator coil 51 should be tightly secured to the inner surface of the housing 50 lest it should be detached therefrom due to vibration and the like when the rotor is rotated at a high speed.
As described above, in order to drive the slot-less motor at a super high speed, an air gap flux density should be relatively sparse, such that, when the stator coil 51 is bonded by impregnation or the like, the air gap flux density must be made to become low while the air gap (d) between the magnet 53 and the stator coil 51 maintain a relatively uniform space therebetween.
However, there is a problem in that, when the slot-less motor is manufactured by the method thus described, and the stator coil is fixed by impregnation, the stator coil is detached from the housing due to low fixing force of the bond and vibration generated in the course of high speed of rotation, or the slot-less motor should be driven at a slower rotating speed in order to prevent the stator coil from being separated from the housing.
In order words, because there is a limit in fixing the coil by way of bond, it is practically impassible to increase the rotating speed of the slot-less motor beyond a predetermined speed limit. Furthermore, as the capacity of the motor is increased, so is the diameter of the stator coil, such that when a separate slot is not available or when the fixing force of the bond does not surpass a predetermined limit, it is difficult to form a coil or to perform the fixing operation. There is still another problem in that a uniform air gap flux density can hardly be obtained when the diameter of the stator coil is increased.